The purpose of the proposed work is to examine alveolar macrophage bactericidal activity against Pseudomonas aeruginosa in normal and cyclophosphamide-induced, bone marrow suppressed donors. Oxidative metabolic mechanisms associated with bactericidal activity will be studied by using chemiluminescence techniques, measuring cellular oxygen consumption, and measuring superoxide anion and hydrogen peroxide generation. Lung macrophages will be studied and compared with peripheral blood granulocytes from the same donors to determine similarities and differences between the two phagocytic cell types. The studies will provide important information about bacterial metabolic mechanisms of phagocytic cells from the lung and peripheral blood in both normal and marrow suppressed donors.